Polythiourea



Patented Mar. 16, 1943 romrrmomtm William Edward Hanfordand Paul L. Sallberg, Wilmington, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application September 15, 1938,

Serial No. 230,145

23 Claims.

The invention relates to synthetic polymeric materials and more particularly to thiocarbamide polymers, 1. e., polythioamides obtainable from polyamines and derivatives of thiocarbonic acid (Boson) s and to the preparation and use of such thiocartion of new and valuable compositions of matter.

Another object is the preparation of synthetic fiber-forming materials. Still another object is the preparation of filaments, fibers, and ribbons from these materials. A further object is the manufacture of yarns, fabrics, and the like from said filaments. Other objects willbecome apparent as the description proceeds.

The first of these objects is accomplished by reacting together a polyamine having at least two hydrogen bearing amino groups which are separated by a chain oi at least 4 atoms in an open chain or of at least 3 atoms, where these form part of one ring or of at least 4 atoms where these form part of two rings, with a thiourea forming derivative of thiocarbonic acid, 1. e. carbonic acid having the :0 replaced by C=S,

under polymerization conditions until a polymeric material is formed.

The second object is accomplished in the same manner as the first object except that the polyamine selectedis a diamine and. in that the polymerization is continued until the resultant polymer exhibits fiber-forming properties.

The third object is attained by spinning the linear polythioureas into filaments, and preferably, subjecting the filaments to stress (cold drawing) thereby converting them into oriented filaments or fibers. The fourth of these objects is accomplished by combining the filaments into a yarn and knitting, weaving, or otherwise forming the yarn into a fabric.

The term synthetic" is used herein to imply that the polythioureas from which the filaments are prepared are built up by a wholly artificial process and not by any natural process. In other words, the original reactants. are monomeric or relatively low molecular weight substances.

The term linear as used herein implies only those poiythioureas obtainable from bifunctional reactants, i. e. from diamines and amidedorming derivatives of thiocarbonic acid. The structural units of such products are linked end-to-end in chain-like fashion. The term is intended to exclude three-dimensional polymeric structure, such as those present in polymers derived from polyamines having more than two hydrogen bearing amino groups.

The term fiber-forming polythiourea" is used to indicate that the products are capable of bein formed directly, 1. e. without further polymerization treatment, into useful fibers. As will be more fully shown hereinafter, fiber-forming polythioureas are highly polymerized products.

The term "filament as used herein refers to both the oriented and unorientcd filaments or threads which are prepared from the polythioureas regardless of whether the filaments or threads are long (continuous) or short (staple), large or small, while the term "fiber will refer more specifically to the oriented filaments or threads whether long or short, large or small.

The term polythiourea is used to indicate a polymeric thioamide containing a plurality of thiourea i groups. In the lineaflpoiythioureas the thiourea groups form a part of the chain of atoms making up said polymer.

By "thiourea-forming derivatives of thiocarbonic acid is meant those materials such as sulfanhydrides, thioamides, acid halides, half esters, and diesters, which are known to form thioureas when reacted with a primary or secondary monoamine.

In order that the consideration of the invention may be clarified the invention will be discussed in its more readily comprehensible and at the same time, its more important aspect, that wherein a diamine is reacted with the thiourea-forming derivative of thiocarbonic acid.

The following discussion will make clear the nature of the products from which the filaments and fibers are prepared, and the meaning of the above and other terms'used hereinafter. If a thiourea-forming derivative of thiocarbonic acid and a diamine are heated together under such conditions as to permit thioruea formation, the reaction might proceed in such a way as to yield a linear polyamide cirns-cs-s-cin5+mNRNm- The indicated formula. in which R represents a. divalent. organic radical, represents the product as being composed of long chains built up from a series of identical units This unit, derived from one molecule each of thiocarbonic acid and diamine, may be called the "structural unit. It will be convenient to refer to the number of atoms in the chain of this unit as the unit lengt Unit length is made up of the radical of thiocarbonic acid,

whose radical length is 1, and the radical of the diamine Thus the radical of pentamethylenediamine is its radical length, i.e. number of atoms in the chain between and including the amino nitrogens, is seven. Consequently the unit length of the polypentamethylenethiourea, the polythiourea derived from thiocarbonic acid and pentamethylenediamine, is eight.

As previously mentioned, fiber-forming polythioureas can be prepared by reacting diamines with thiourea-forming derivatives of thiocarbonic acid, of which the most suitable are the 'diesters with volatile monohydric alcohols or .er melting points. Within the field of di-primary diamines, those most suitable for the ready preparation of polythioureas capable of being drawn into the highest quality fibers are those diamines in which the amino nitrogens are attached to aliphatic carbons, (i. e. carbon atoms which are not a part of an aromatic ring). Mixtures of diamines of any of the mentioned operable types may also be used. Fiber-forming polythioureas may also be prepared from one or more diamines and ((1) mixtures of thiourea-forming derivatives of thiocarbonic acid or (b) mixtures of thiourea-forming derivatives of thiocarbonic acid with one or more monoaminomonocarbothionic acids or thioamide-forming derivatives thereof.

While the fiber-forming polyamides used in the invention can be prepared from a wide variety of diamines andthiourea-forming derivatives of thiocarbonic acid, a preferred selection of amine and thiourea-forming derivative of thiocarbonic acid is that in which the sum of the radical lengths is at least 9. Such a pair of reactants has very little if any tendency to form low molecular weight cyclic thioureas and the polythioureas therefrom are more generally soluble or fusible, one of these properties being necessary for spinning. Some success has been attained,

ureas from'amines and thiourea-forming derivatlves of thiocarbonic acidwhere the sum of the radical lengths is less than 9. A I

0f thefiber-forming polythioureas having a unit length of at least 9, a very useful group, from the standpoint of fiber qualities, are those derived from diamines of formula in which 'R is a divalent organic radical having a radical length of at least four atoms. Preferably R is a hydrocarbon radical, e. g., an aliphatic, alicyclic, aromatic, or araliphatic radical. Of this group of polythioureas those in which R is (CH-an where a: is an integer and is at least 4 are especially useful from the standpoint of spinnability and fiber qualities. They are easily obtained at an appropriate viscosity for spinning and have a type of crystallinity which enables them to be cold drawn with especial facility. As valuable members of these classes may be mentioned polyhexamethylenethiourea, polyoctamethylenethiourea, polyoctadecamethylenethiourea and polyxylenethiourea.

The fiber-forming polythioureas are prepared by heating in substantially equimolecular amounts a diamine and a thiourea-forming derivative of thiocarbonic acid under polymerization conditions generally 100 to 250 C., in the presence or absence of a diluent, preferably a phenol, until the product has a suficiently high molecular weight to exhibit fiber-forming properties. The fiber-forming stage can .be tested for by touching the molten polymer with a rod and drawing the rod away; if this stage has been reached, a continuous filament of considerable strength and pliability is readily formed. This stage is reached essentially when the polyamide has an intrinsic viscosity of about 0.12, where intrinsic viscosity is defined as in which a is the viscosity of a dilute solution (e. g., 0.5% concentration) of the polymer in m-cresol divided by the viscosity of m-cresol in the same units and at the same temperature (e. g., 25 centigrade) and C is the concentration in grams of 'polymer'per 100 cc. of solution, If products capable of being formed into fibers of optimum quality are to be obtained, it is desirable to prolong the heating beyond that point where the intrinsic viscosity has become 0.12. In general products having an intrinsic viscosity between 0.18 and 1.0 are most useful for the preparation of fibers. The polythioureas become fiber-forming at much lower intrinsic viscosities than do most other linear polymers.

The reactions are preferably conducted in the absence of oxygen which may be accomplished either by operating in vacuum or in the presence, of an inert gas such as nitrogen. Although the preferred embodiment comprises heating the re,-

. actants until they exhibit fiber-forming properhowever, in preparing fiber-forming polythioti es, it is within the scope of this invention to discontinue heating before this stage is reached.

The low molecular weight or non-fiber-forming polymers are useful for certain applications, e. g., molding compositions or adhesives.

In common with other polymerization products the fiber-forming polythioureas will in general comprise a series of individuals of closely similar structure. The average size of these individuals, i. e., the average molecular weight of the polymer is subject to deliberate control within certain bilizer.

asraan limits: the further the reaction has progressed the higher the average molecular weight (and in-'- trinsic viscosity) will be. If the reactants are used inexactly equimolecular amounts and the heating is continued for a long time under conditions which permit the escape of the volatile products, polythioureas of very high molecular weight are obtained. However, if either reactant is used in excess, the polymerization proceeds to a certain point and then essentially stops. The point at which polymerization ceases is dependent upon the amount of diamineor thiocarbonic acid derivative used in excess. The reactant added in excess is spoken of as a viscosity stabilizer" and the polymer obtained with its use is spoken of as a viscosity stable polymer, since its intrinsic viscosity is not altered appreciably by further heating at spinning temperatures. Polythioureas of almost any intrinsic viscosity can be prepared by selecting the proper amount of sta- In general from 0.1 to 5.0% excess reactant is used in making viscosity stable polythioureas. Monoamines and monocarboxylic acids can also be used as viscosity stabilizers. The viscosity stable polythioureas are particularly useful in spinning filaments from melt since they do not change appreciably in viscosity during the course of the spinning operation.

The reaction between the diamine and the thiourea-forming derivative of thiocarbonic acid may be carried out in the absence of a solvent, in the presence of a solvent, in the presence of a diluent which is not a solvent for the polymer or in the presence of a mixture of solvent and diluent. The reaction conditions differ somewhat with the nature of the thiourea-forming derivative used.

'For example, esters of trithiocarbonic acid often bonate) generally does not react below 100 C.

The polythioureas of this invention compared with most organic compounds are fairly resistant to oxidation. Nevertheless, at high temperatures they show a tendency to become discolored in the presence of air. For this reason, it is desirable to exclude air or to limit the access of airduring their preparation. This may be done by operating in a closed vessel during the early stages of the reaction,- or, if an open vessel is used, by pro viding a stream of inert gas. It is helpful in some cases to add'antioxidants to the reaction mixture, especially antioxidants such as syringic acid that show very little inherent tendency to discolor. It is also desirable to exclude oxygen from the polymer during spinning.

the surface of .the reaction vessel (e. g. glass) appears to exercise a certain degree of catalytic function in many cases. The use of added catalysts sometimes confers additional advantages. Sulfur, for example, is a suitable catalyst.

The polythioureas can be prepared in reactors constructed of or lined with glass, porcelain, enamel, silver, gold, tantalum, platinum, palladium, rhodium, alloys of platinum with palladium and/or rhodium, chromiumplated metals, and chromium containing ferrous metals, including chromium-nickel steels. In order to obtain lightcolored products it is generally necessary to carry out the reaction in substantially complete absence of oxygen. This means that if commercial nitrogen is maintained over or passed through the reaction mixture it should be washed free of oxygen. As examples of other inert gases which may be used toblanket the polymer during pr naration or spinning may be mentioned argon, helium and hydrogen.

In the finely divided state or in the form of filaments and fibers the polythioureas of this invention are attacked by strong mineral acids, such as hydrochloric or sulfuric acid, and on heating with such acids they are hrydrolyzed to carbon dioxide, hydrogen sulfide and the diamines from which they are-derived. When reference is made in the claims to the formation of a diamine" by acid hydrolysis, it is to be understood that the term includes the mineral acid salt of the diamine. 'The polythioureas are resistant to attack by strong caustic alkalies but these agents also will finally hydrolyze them to the diamines an'd thiocarbonate salts.

The linear polythioureas of this invention can be spun into continuous filaments in a number of ways. They can be spun directly from the reaction vessel in which they are prepared by attaching a suitable spinneret to the bottom thereof or they can be removed and spun from a separate device. One method of spinnin (wet process) consists in dissolving the polythiourea in a suitable solvent and extruding the resulting solution through orifices into a liquid which dissolves the solvent but not the polythiourea and continuously collecting the filaments thus formed on a suitable revolving drum or spindle. Another method (dry process) consists in extruding a solution of the polythiourea into a heated chamber where the solvent is removed by evaporation. Still another method (melt process) consists in extruding the molten polythiourea throughorifices into the atmosphere where it congeals into a filament. In these various methods of spinning the fiberforming mass may be forced through the orifices by means of a gas or delivery pump.

It is advantageous to subject the filaments to a cold drawing process (i. e., stretching below the melting point of filament) By this cold drawing the filaments can be elongated as much as to 800%. The elongation is accompanied by a progressive increase in tensile strength until a definite limit is reached beyond which the application of additional stress causes the fiber to break. The cold-drawn filaments remain permanently extended, they are much stronger than the material from which they are drawn, and are more elastic. When examined by X-rays they furnish a sharp diifraction fiber pattern. They also exhibit strong birefringence and parallel extinction when observed under crossed Nicol prisms. This evidence of fiber orientation shows that the cold drawn filaments are true fibers. The fibers can be doubled and/or twisted into threads or yarns suitable for the manufacture of fabrics. Sometimes it is desirable to set the twist in these yarns by means of heat, preferably by steam treatment. If desired, the filaments used in the preparation of the fibers can be twisted before cold drawing.

As already indicated the linear polythioureas of this invention are of such a nature that they are capable of being spun into continuous filaments directly from the molten mass without addition of any solvent or plasticizer. Thus continuous filaments may be produced by extruding the molten polythiourea through an orifice, or through a spinneret containing a plurality of orifices, and continuously collecting the extruded filaments on a rotating drum. The fineness of the filaments may be controlled by controlling the temperature of the molten polymer, the

less. The optimum temperature for the spinning of each polythiour'ea must be worked out experimentally. Below this optimum temperature filaments of inferior quality are obtained; above this temperature the polythiourea mass is too fluid for ready spinning and may be subject to decomposition. In spinning the polythioureas from melt it is also desirable that oxygen be excluded from the molten polymer.

In the melt spinning process the formation of continuous oriented fibers from the filaments of this invention may be conducted as an integral part of the spinning operation. Thus, the extruded filaments as they are collected may be transferred continuously to a second drum driven at a higher rate of speed, so as to provide any desired degree of stretching or cold drawing.

The properties of the fibers of this invention vary considerably with the nature of the reactants used in preparing the polythioureas, and with the conditions of reaction and spinning. General characteristics are high tenacity, lack of sensitivity toward conditions of humidity, good resistance to-solvents and chemical agents and good ageing characteristics.

In the preparation of the polymers of the present invention various thiourea-forming derivaceedingly fine filaments, as fine as 0.5 denier or v tives of thiocarbonic acid may be reacted with various primary and secondary polyamines. The

examples which follow disclose primary diamines METHOD A In the first method of practicing the invention substantially chemically equivalent quantities of an ester of trithiocarbonic acid and a polyamine and preferably a diamine as described above are reacted at such a temperature and under such conditions that the volatile by-products, a mercaptan or mercaptans, are allowed 7 to escape. Ethyl methyl trithiocarbonate CHaCHzSCSCHa i has been used because of its ease of preparation. The reactants are preferably mixed at room temperature and warmed slightly until a homogeneous solution is formed. This solution is then heated for about one hour at 90 C. to 110 C., during which time the reaction mixture usually solidifies. This material is then heated at 130 C. to 135 C. for four to five hours. The preliminary heating at 90 C. to 110 C. may be omitted if desired and the final heating need not be within the limit of 130 C. to 135 C. if proper allowance in length of time of heating is made to compensate for deviation from these limits. For example, 45 minutes heating at 150 C. is approximately equivalent to five hours heating at 135 C. All heating may be done in an open vessel but is preferably done in an atmosphere of an inert gas such as nitrogen. A solvent such as phenol may be employed if desired. The reaction involved is exemplified as follows:

wherein HzNRNH: is a primary diamine and R are univalent hydrocarbon radicals.

and R which may be the same or different.

The following examples, in which the quanti ties of reactants are parts by weight, are illustrative of this method for preparing linear thiocarbamide polymers.

Example I the temperature being allowed to increase to 25,

C. After two hours the oily layer which separates is removed, the aqueous layer is extracted with ether, and the oily layer and the ether extracts are combined and dried over calcium chloride. methyl trithiocarbonate, an orange liquid boiling at 82-85 C./3 mm., N 1.6441.

Anal. Calcd for C4H8S32 S, 63.16%. S, 63.08%.

Polydecamethylenethiourea is prepared by dissolving 1'70 parts of decamethylenediamine in 150 parts of ethyl methyl trithiocarbonate' and heating for one hour at C. Ethyl and methyl mercaptans a're evolved, and the mass sets to a crumbly solid. This low molecular weight polymer is then heated for five hours at l30-135 C. All heating is done under an atmosphere of nitrogen scrubbed by bubbling through sodium anthraquinone-fl-sulfonate alkaline hydrosulfite solution. After cooling, the resultant high polymer is removed from the vessel.

The polymer so obtained, polydecamethylenethiourea is a porous hard, tough, almost white polymer, softening at about C. and melting about C.

Analysis: Calculated for C11H22N2S: S,14.95%. Found: S, 15.67%.

It is soluble in phenol, the cresols, hot benzyl alcohol, and hot aniline. The intrinsic viscosity of the polymer is 0.30. When the poly mer is heated to about 180 C. a glass rod can be touched to the semi-molten mass and a filament formed when the rod is drawn away. This fiber can be cold drawn until the length of the fiber is increased by from 20 to 60 per cent of its original length.

Polydecamethylenethiourea may be cast into sheets by squeezing the massive polymer between plates covered with aluminum foil and mounted in an electrically heated press at 120-130 C.

Found Pressure is applied slowly, an increase of 1000 tensile strength of 10,800 lbs./sq. in. After 3, months exposure to outdoor winter conditions,

the sheeting does not lose more than 20 to 30 per cent of its original strength. Freshly prepared sheeting can be cold-rolled to twice itsoriginal area but retracts to its initial size in about twelve hours at room temperature or immediately at 100 C. Sheeting that has retracted after cold rolling has a tensile strength of about 7500 lbs./sq. in.

Distillation gives 38 parts of ethyl carbamate in substantially the same manner as described above, is a tough, spongy, almost white polymer, softening at about 140 C. and melting about 220 C. It is soluble hot in formic acid, phenol, ethylene chlorhydrin, aniline, or cresol. Evaporation at 100 C. of either the formic acid or the ethylene chlorohydrin solution gives a hard, glossy film adhering well to glass. The intrinsic viscosity of the polymer, determined in cresol is 0.28. When the polymer is heated to about 220 C. a fiber can be drawn by touching and withdrawing a glass rod from the semi-molten mass. This fiber can be cold-drawn until th length of the fiber is increased by from 20 to 60 per cent of its original length.

Sheets prepared from the polyh'examethylenethiourea are prepared by squeezing massive polymer between plates covered with aluminum foil and mounted in an electrically heated press at Mil-145 C. Pressure is applied slowly, an increase of 1000 lbs/sq. in. being applied each fifteen seconds until 10,000 lbs/sq. in. was reached.

This pressure is held for two minutes. The resulting sheet is removed and pressed between fresh aluminum foil 'for five minutes under 14,000 lbs. pressure, likewise attained by applying pressure at the rate of 1000 lbs/sq. in. every fifteen seconds. This last step is then repeated twice more. Sheets so prepared are clear and colorless and have an excellent surface nearly free from flaws. The sheeting has a tensile strength of 8,200 lbs./sq. in. and can be cold-rolled to 200 per cent of its original area. After rolling, the sheeting has a tensile strength of 11,400 lbs/sq. in. Cold rolled sheets retract immediately at 100 C. to their original dimensions but do not retract at room temperature. Neither the cold-- rolled nor the unrolled sheeting lose more than 20-30 per cent of its original strength by three months outdoor exposure.

By a modification of the foregoing procedure, two or more different diamines may be incorporated in the polymer. Either th mixture of diamines can be reacted directly with the trithiocarbonate or a trithiocarbonate and less than the chemically equivalent amount of a diamine may be heated together for several hours at from 130 to 135 C. Sufficient amounts of the other diamine or diamines may then be added to make the total amount of diamine used chemically equivalent to the total amountbf trithiocarbonate taken originally. The mixture is again heated for a suitable length of time to form a polymer possessing the desired physical properties. Example II To 13.78 parts of meta-phenylenediamine is added 19.42 parts of ethyl methyl trithiocarbonate. The mixture is heated for 1.5 hours at 120 C. to 140 C., during which time ahomogeneous solution is formed. This is heated 8 hours at 170 C. to 180 C. after which no more mercaptan is evolved. The product is an orange colored, brittle, porous polymer softening at 150 C. andmelting at 200 C.. Poly-m-phenylenethiourea has an intrinsic viscosity, as determined in cresol, of 0.06 and can be transformed into brittle filaments in themanner described under Example I. The polymer can be pressed to clear, brittle sheeting at 145 C. under'4000 lbs/sq. in. pressure.

Anal. Calcd for C'1HsN2S: S, 21.36. Found:

Meta-phenylenethiourea can be prepared in phenol solution by adding 18 parts of crystalline phenol to the above quantity of ingredients, increasing the heating at 170 C. to 180 C. by 6 hours, and precipitating the polymer by pouring the phenol solution at C. into 285 parts of commercial ethanol. Poly-m-phenylenethiourea so prepared has the same appearance and fiberforming properties as polymer prepared without solvent. It softens at 230 0., melts at 265 C., and can be pressed into sheeting at 230 C. The intrinsic viscosity of this polymer, as determined in cresol, is 0.06.

The following' Examples III and IV illustrate the use of a solvent in the preparation of the polymer by' Method A:

. Example III To 17.5 parts of ethyl methyl trithiocarbonate is added 19.8 parts of decamethylenediamine. After standing one hour at room temperature, the mixture is dissolved in phenol (10 parts) by warming at C. for about 45 minutes. The solution is heated for one hour. at C. under atmospheric pressure and then heated an additional hour at about the same temperature under 25 mm. pressure with gentle reflux. Finally, heating is completed at approximately 130 C./3 mm. to remove the phenol. The polymer is an almost colorless, translucent, hornymass which softens at 100 C. and can be drawn into filaments at 185 C. These filaments can be cold drawn to a 20 to 30 per cent increase in length. The intrinsic viscosity of the polymer, determined-in m-cresol, is 0.14.

Anal. Calcd for C11H22N2S: S, 14.95%. Formd: S, 14.85%

Example IV To 62.10 parts of meta-phenylenediamine is added 160.5 parts of ethyl methyl trithiocarbonate and 130 parts of crystalline phenol. The mixture is heated at 100 C. until thoroughly dissolved and at C. to C. for 12 hours. Decamethylenediamine (87.92 parts) is then added and heating is continued at 130 C. to 140 C. for 7 hours. The polymer is precipitated by pouring the phenol solution into several hundred parts of well agitated, commercial ethanol. Poly-m-phenylene polydecamethylenethiourea so prepared is a light colored product softening at 90 C. and melting at 130 C. It can be transformed into brittle filaments in the manner described under Example I.

Method B from 100 C. to 180 0., preferably until a test portion indicates that the resultant polymer has I ited by, the to in the parts are by weight.

acquired fiberor film-forming properties. The reaction maybe represented as follows:

wherein HzNRNRHa is a diamine as described previously.

This metho wing illustrative example where- Emample V To 10 parts' of carbon disulfide in 80 parts of .methanol is'added dropwise 15.3 parts of hexamethylenediamine. in'80 parts 'of methanol at is illustrated by, but not um 0 C. with stirring: The carbon disulfide-hexamethylenediamine salt separates almost imme-' diately. The suspension is stirred for two hours at room temperature after the addition is complete and is then filtered. The salt is air-dried and used in the following polymerization.

Three parts of air-dried salt is mixed with 0.0-3 part of powdered sulfur as a catalyst and heated'at 125-135 C. for four and one-half hours in a sealed vessel with 0.7 part of crystalline phenol. The vessel is cooled and opened, and the reaction mixture is ground in a mortar with commercial ethyl acetate to remove the phenol." Removal of the solvent by filtration gives 'a lightcolored polymer which, when melted and touched with a cold rod, gives a continuous filament on drawing the rod away. Pressed under 2000 lbs/sq. in. at 125 C. for one minute, the polymer forms a clear, though somewhat yellowsheet.

' Mzmon C In this third method of practicing the invention, substantially chemically equivalent quantities of a polyamine, e. g. a 'diamine as described above and a bis(dithioca'rbamate) oi the general wherein HzNRNI-Ia and R, R and R" are as defined above. If the group R in thediamine and the group R in the.bis(dithiocarbamate) are not the same. a polymer will result having two different radicals inthe recurring structural unit.

This method is illustrated by. but not limited by, the following illustrative examples wherein the parts are by weight.

Example VI In 300 parts ofwater is dissolved 34.8 parts of hexamethylenediamine and 32.2 parts of potassium hydroxide. To this 50.2 parts of carbon disulflde is. added at room temperature with stirring. No odor of diamine or carbon disulfide can bedetected after one hour. Dimethyl sulfate (78.2 parts) is added dropwise with stirring at 20 C. An additional 300 parts of water is added.

. the slurry stirred two hours at 20 to 30C. and

tral to litmus. air-dried and recrystallized from methanol (3.2 partsof methanol per quart of product. The compound is redissolved in 270 f 'parts ofbenzene, decanted from insoluble material, and partly precipitated by adding 20 parts of petroleum ether (B. P. 40-60 C.) to the hot benzene solution; The crystalline product melts at -125 C. The benzene filtrate is heated to boiling and petroleum ether added until turbidity resulted. The second crop of dimethyl hexamethylene bis(dithiocarbamate), obtained by cooling the' benzene-petroleum ether solution to 20 C., melts at 124.5-126 C. a

In a reaction vessel are mixed 34.2 parts of ments only. Accordingly, the polymer is heated for one hour at 130 C. to C. under 2 mm.

pressureto remove traces-of phenol. The polymer then softens at 95 C. and can be drawn to continuous filaments at 215 C. The intrinsic.

viscosity of this polymer, determined in m-cresol, is 0.12. Massive polymer can be pressed at about 140 C. to clear sheeting having a tensile strength of about .4700 lbs/sq. in. These sheets can be cold-rolled to 250 per cent of their original area. The resulting films show increased clarity, brilliance, and stifl'ness. Within two. or three days, these cold-rolled sheets retract to their original dimensions and have tensile strengths of about 4900 lbs/sq. in.

- Mrznron D In this fourth method of practicing the invention chemically equivalent quantities of a diamine as described above and ammonium thiocyanate are heated together, following a suitable heating schedule to obtain a similar polymer. The reactions involved may be expressed as follows: I

wherein HzNRNHz is as described heretofore. A suitable'heating schedule is one that allows Reaction 1' to proceed without frothing and then allows Reaction 2 to proceed to fiber-forming polymer without causing excessive decomposition.

For example, one hour at 60-120" C. and 30 min utes at C. should be suitable. The rearrangement or dearrangement of ammonium thiocyanate'to thiourea is a well-known chemical change.

This method is illustrated by, but not limited by, the following illustrative examples wherein the parts are by weight.

. Example VII.

To decamethylenediamine (7.130 parts) is added ammonium thiocyanate (3.150 parts) with thorough mixing. -In the course of one hour the mixture is heated from room temperature to 200 C. at which temperature the melt is held for about ten minutes. When cooled, the poly mer is transparent, light-colored, flexible, tough inthe massive state, softens at about 80 C. and melts at about 115 C. When melted, filaments can be drawn from the molten mass. The intrinsic viscosity of this polymer, determined in m-cresol, is 0.14.

, Marnon E.

, A still further method rather similar to that given above is the reaction of a polyamine and a polyisothiocyanate, preferably a diamine and a To 7.95 parts of 'decamethylene diisothiocya- 'nate in 140 parts ofether is added 5.34 parts of decamethylenediamine in 59 parts of ether. The white precipitate which separates after a short time is filtered off and washed with ether, 12 parts being obtained. It is insoluble in alcohol, soluble in m-cresol, melts at 115 C., and is presumably a low polymer. To effect further polymerization,-it is dissolved in 15 parts of cresol and heated 8 hours at 200 C., during which time some hydrogen sulfide is evolved. The cresol solution is washed with alcohol, giving a product which still melts at 115 C. and which has an intrinsic viscosity of 0.31. When fused, the polymer can be drawn to an elastic filament by touching with a cold rod and removing the rod. The

-flber-forming product is obtained.

polymer is insoluble in dilute sodium hydroxide,

dilute hydrochloric acid, and glacial acetic acid.

In general the polythioureas of the present invention contain a recurrent structural unit of the formula ganic radical which is derived from the polyamine by the subtraction therefrom of its hydrogen bearing amino groups. In the linear polymers which form the preferred, because the more important class of the present invention, R is divalent and may be aliphatic, aromatic, alicyclic, or heterocyclic, saturated or unsaturated. It must contain no groups which, under the conditions used, react with the diamines or the thiocarbamide-formi'ng derivative of trithiocarbonic acid being employed.

It can be readily seen from the examples that an important feature of the process of this invention is that the diamine and thiourea-forming derivative are eventually reacted or the low molecular weight non-fiber-forming polythlourea therefrom is further reacted under conditions which permit the formation of a very highly condensed polythiourea. In other words, the heating must be continued at such a. temperature and for such a period of time that the product can be drawn into oriented fibers, and this point is reached essentially only when the intrinsic viscosity has risen to at least 0.12. In the preparation of some of the new fiber-forming polythlourea, it may be advantageous to apply the principles of moleculardistillation described in U. S. 2,071,250.

It will be also noted from theexamples that the process of the present invention comprises certain stages including the reaction of the polyamine with the thiourea-forming derivative of thiocarbonic acid, the polymerization of the product to a more or less low molecular weight polymer and finally-the further step which need molecular weight, fiber-forming. polythlourea.

This modification is exemplified above particularly in Example I. In certain other examples, the first stage-the reaction of the diamine and thioamide-forming derivative of thiourea-is indicated but the formation of the low polymer is not separated from the formation of the fiberforming or superpolymer. In other examples, e. g. Example VII, the process is not separated into any stages but is an integral one.

The formation of a superpolym'er" from the lower molecular weight polymer of. course takes place in all of these modifications wherein a In view of the high utility of the superpolymers, the conversion of low polymer to superpolymer is a part .of the preferred embodiment of the invention.

.While the preceding discussion has gone into detail with respect to the reaction of'the primary diamines with the thiourea-forming derivatives of thiocarbonic acid, the invention is generic to and the processes above detailed with respect to diamines may be applied to polyamines, stoichiometric quantities of reactants being employed. Thus there may be employed diethylenetriamine, triethylenetetramine and di(hexamethylene)triamine. It is thus generic to the reaction of primary and secondary polyamines including aliphatic, aromatic, alicyclic, heterocyclic, unsatu- (HaNCHzCHzOCHzCHzOCHzCI-IzNI-Ia) or thiodiglycoldiamine (HaNCHzCHzSCI-IaCHzNHz) The polyamine must, however, have a chain of at least four atoms between amino nitrogens when the chain is an open chain, and at least three atoms where these form part of one ring and at least four atoms when these form part of a plurality of rings. As indicated above, the amide (thiourea and its equivalent ammonium thiocyanate) the esters, the thioanhydride, thiocarbamic' acid, thiophosgene or in general any thiourea-forming derivative of thiocarbonic acid may be used. The esters preferably form volatile mercaptans.

While filaments of small diameter (0.00015- 0.00l5 inch, corresponding roughly to 0.110.0 denier) are the most useful for the preparation of yarns and fabrics, filaments of other sizes can be prepared from the polythioureas of this invention. For example, it is possible to prepare larger filaments (e. g. 0.0015-0.1) which are useful as bristles, artificial straw, horse hair substitutes, and the like from the fiber-forming polythioureas by the methods herein described.

It is to be understood that the invention comprises also fibers, etc. prepared from interpolythioureas, e. g., a polythlourea derived from the reaction of two or more diamines with thioureaforming derivatives of thiocarbonic acid. The

m-phenylenediarnine,

fibers can also be prepared from mixtures of prepolythiourea or polythiourea solution containing dispersed therein a finely divided substance which is inert toward the polythiourea, is incompatible therewith at ordinary temperatures, and has an index of refraction differing from that of the polythiourea. Pigment-like materials are generally good delusterants. As examples of suchdelusterants might .be mentioned titanium di- I oxide, zinc oxide, zinc sulfide, barium sulfate,

carbon black, and copper phthalocyanine' pigment. However, many organic compounds, e. g., non-phenolic polynuclear compounds, also function as delusterants.

It will be apparent that the polythioureas herein described are most useful in the form of filaments and fibers. Many other valuable artificially shaped objects may, however, be prepared from by suitable modification of the general methods herein described. For example, films,

' foils, sheets, ribbons, bands, rods, hollow tubing,

and the like can also be prepared from them. They are particularly suitable for interlayers in safety glass because they adhere to the glass very tenaciously. The polymers may be used either alone or in admixtures, as with plasticizers, resins, dyes, pigments, etc. They can aslo be used in molding andcoating compositions,

The tough, transparent films prepared from these polymers have unusually high tensile strengths per unit of cross sectional area and in some instances these tensile strengths may be increased by coldmrollihg. The polymers show unusually strong adherence to glass without the use of adhesives and are also slightly, softened atthe higher temperatures met in safety glass applications. The films are not embrittled at the lower temperatures.

The polythioureas are also of value in improving the properties of fibers and the like derived from synthetic linear polyamides. For example, the addition of 1.0% by weight ofa polythiourea to fibers of polymeric hexamethyleneadipamide markedly improves the ageing qualities (retention of strength) on outdoor'exposure.

The above description and examples are intended to be illustrative only. Any modification of or variation therefrom whichconforms to the spirit of the invention is intended to be included within the scope of the claims.

We claim:

1. A linear polythiourea having recurring structural units of the general formula N(B)RN(B')CS- wherein B and B' are members of the class consisting of hydrogen and monovalent hydrocarbon radicals and R is a divalent organic radical in which the terminal atoms are carbon, which is free from groups reactive with the amino, thioanhydride, acid halide, ester, and amido groups, and which contains a chain of atoms selected from the'classconsisting' of chains of at least four atoms in an open chain, chains of at least four atoms forming part of a plurality of rings,

and chains of at least three atoms forming part of one ring.

wherein B and B' are members of the class consisting of hydrogen and monovalent hydrocarbon radicals and R is a divalent organic radical in which the terminal atoms are carbon, which is free from groups reactive with the amino, thioanhydride, acid halide, ester, and amido groups, and which contains a chain of atoms selected from the class consisting of chains of at least four atoms in an open chain, chains of at least four atoms forming part of a plurality of rings, and chains of at least three atoms forming part' of one ring, said polythiourea being one which can be formed into filaments capable of being cold drawn.

i). A linear polythiourea having recurring structural units of the general formula wherein R is a divalent hydrocarbon radical which contains a chain of atoms selected from the class consisting of chains of at least four atoms in an open chain, chains of at least four atoms forming part of a plurality of rings and chains of at least three atoms forming "part of one ring, said polythiourea being one which can be formed into filaments capable of being cold drawn.

4. Method of making polymers which comprises heating a polyamine having at least two hydrogen bearing amino nitrogen atoms and selected from the class consisting of polyamines wherein the hydrogen bearing amino nitrogen atoms are separated by a chain of at least four atoms in an open chain, polyamines wherein the amino nitrogen atoms are separated by a chain of at least four atoms forming part of a plurality of'rings, and polyamines wherein the hydrogen bearing amino nitrogen atoms are separated by a chain of at least three atoms forming part of one ring, with a thiourea-forming derivative of thiocarbonic acid of the class consisting of the thioanhydride, acid halides, esters, and amides of said acid at a temperature within the range C. to 250 C. until the produot'exhibits an I intrinsic viscosity of at least 0.12.

5. Method of making polymers which Cora prises reacting, by heating, a primary diamine selected from the class consisting of polyamines wherein the hydrogen bearing amino nitrogen atoms are separated by a chain of at least four atoms in an open chain, polyamines wherein the hydrogen bearing amino nitrogen atoms are separated by a chain of at least four atoms forming part of a plurality of rings, and polyamines wherein the hydrogen bearing amino nitrogen atoms are separated by a chain of at least three atoms forming part of one ring with a thioamideforming derivative of thiocarbonic acid of the class consisting of the thicanhydride, acid halides, esters, and amides of said acid at a temperature within the range 100 C. to 250 C. until the product exhibits fiber-forming properties.

6. Method of making superpolymers which comprises heating a low molecular weight nonfiber-forming polymeric polythiourea at 100-250 C. until a high molecular weight fiber-forming polymeric polythiourea is formed as evidenced by the formation of a continuous filament when the molten polymer is touched with a rod and the rod drawn away said polymeric polythiourea having recurring structural units of the'general formula anhydride, acid halide, ester, and amido groups,

and. which contains a chain of atoms selected from the class consisting oi chains of at least four atoms in an open chain, chains of at least four atoms forming part of a plurality of rings.

.and chains of at least three atoms forming part of one ring.

'LMethod of making superpolymers' which comprises heating a low molecular weight nonfiber-forming polymeric polythiourea at 100-250" C. until a high molecular weight fiber-forming polymeric polythiourea is formed as evidenced by the formation of a continuous filament when the molten polymer is touched with a rod and the rod drawn away, said polythiourea having recurring structural units of the general formula wherein R is a divalent hydrocarbon radical which contains a chain of atoms selected from the class consisting of chains of at least four atoms in an open chain, chains of at least four wherein R is a divalent hydrocarbon radical which contains a chain of atoms selected from the class consisting of chains of at least four atoms in an open chain, chains of at least four atoms forming part of 'a plurality of rings and chains of at least three atoms forming part of one'ring, said polythiourea being one which can be formed into filaments capable of being cold drawn.

9. Method of making polymers which com prises reacting a diamine having a bivalent hydrocarbon chain of at least four atoms between the .two amino groups, each of which has at least one hydrogen on the nitrogen, with a hydrocarbon diisothiocyanate at a temperature within the range 100 C. to 250 C. until the product exhibits an intrinsic viscosity of at least 0.12.

10. Polydecamethylenethiourea.

11. Polyhexamethylenethiourea.

12. Poly-m-phenylenethiourea.

13. A polymeric thiourea having the recurring thiocarbonyl groups separated by polyamido radicals having terminal amido nitrogens, in turn attached to carbon, and a radical length of at least eight, the valences of said terminal amido nitrogens not satisfied by chain carbons being satisfied by members of the class consisting of hydrogen and monovalent hydrocarbon radicals and the polyamido radicals 7 being free from groups reactive with the amino, thioanhydride, acid halide, ester, and amido groups.

14. A linear polymeric thiourea having the recurring thiourea -NH--CSNH groups separated by bivalent chains whose free valences stem from carbon and which are selected from the class consisting of open chains of at least four atoms, chains of at least four atoms forming part of a plurality of rings and chains of at least three atoms forming part of but one ring, said polymeric thiourea having an intrinsic viscosity of at least 0.12.

15. A synthetic polymer in the form of a pliable filament,

--NHCSNH- groups separated by bivalent chains whose free valences stem from carbon and which are selected from the class consisting of open chains of at least four atoms, chains of at least'four atoms forming part of a plurality of rings and chains of at least three atoms forming part of but one ring.

16. A synthetic polymer in the form of a p11- able artificial fiber showing by characteristic X-ray patterns orientation along the fiber axis, said polymerbeing a polymeric thiourea having the recurring thiourea -NH--CS-NH-- groups separated by bivalent chains whose free valences stem from carbon and which are selected from the class consisting of open chains of at least four atoms, chains of at least four atoms forming part of a plurality of rings and chains of at least three atoms forming part of but one ring.

17. A fabric comprising synthetic polythiourea filaments, said polythiourea having the recurring thiourea NHCS-NH groups separated by bivalent chains whose free valences stem from carbon and which are selected from the class consisting of open chains of at least four atoms, chains of at least four atoms forming part of a plurality of rings and chains of at least three atoms forming part of but one ring.

18. A synthetic polythiourea in the form of a film, said polythiourea having the recurring thiourea NHCS--NH groups separated by bivalent chains whose free valences stem from carbon and which are selected from the class consisting of open chains of at least four atoms, chains of at least four atoms forming part of a plurality of rings and chains of at least three atoms forming part of but one ring.

19. A polymeric thiourea having the thiocar of said terminal amido nitrogens not satisfied by chain carbons being satisfied by members of the class consisting of hydrogen and monovalent hydrocarbon radicals.

20. A polymeric thiourea having the recurring thiourea NHCSNH groups joined by polymethylene chains of at least four carbon atoms.

21. An article of manufacture comprising a synthetic linear polythiourea having recurring structural units of the general formula amino, thloanhydride, acid halide, ester, and

amido groups and which contains a chain, hav-- ing terminal carbon atoms, selected from they said polymer being a poly-' V meric thiourea having the recurring thiourea.

class consisting of open chains of at least four, atoms, chains of at least four atoms forming part of a plurality of rings and chains of at least three atoms forming part of but one ring.

22. A polymeric thiourea having recurring thiourea NH-CSNH- groups separated by a bivalent hydrocarbon radical having a chain of at least four atoms between the free valences.

23. A polymeric thiourea having the recurrlng' thiourea NH-CSNH groups separated by a bivalent hydrocarbon radical having between a the free valences achain selected from the group consisting of open chains of at least four atoms, chains of at-least four atoms formingpart of a plurality of rings and chains, of at least three atoms forming part of but one ring.

WILLIAM EDWARD HANFORD. PAUL L. SALZBERG. 

